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The detection of common diodes (including detector diodes, rectifier diodes, damper diodes, switching diodes, freewheeling diodes) is a semiconductor device formed of a PN structure with unidirectional conduction characteristics. By detecting the positive and negative resistance values with a multimeter, the electrode of the diode can be discriminated, and the diode can be estimated to be damaged.
1. Polarity discrimination Place the multimeter in R×100 file or R×1k file. The two test leads are connected to the two electrodes of the diode. After measuring one result, adjust the two test leads and measure one result. Of the results of the two measurements, one measured a larger value (which is a reverse resistance) and one measured a smaller value (which is a forward resistance). In a measurement with a small resistance value, the black meter is connected to the anode of the diode, and the red meter is connected to the cathode of the diode.
2. Detection of single negative conductivity and judgment of good or bad Generally, the forward resistance of the germanium material diode is about 1kΩ, and the reverse resistance is about 300. The silicon material diode has a resistance value of about 5 kΩ and a reverse resistance value of ∞ (infinity). The smaller the forward resistance, the better, and the larger the reverse resistance, the better. The difference between the positive and negative resistance values is different, indicating that the unidirectional conduction characteristics of the diode are better. If the measured forward and reverse resistance values of the diode are close to 0 or the resistance is small, it indicates that the diode has a breakdown short circuit or leakage damage. If the measured forward and reverse resistance values of the diode are infinite, the diode is open circuit damaged.
3. Reverse breakdown voltage detection diode reverse breakdown voltage (withstand voltage value) can be measured with the transistor DC parameter test chart. The method is as follows: when measuring the diode, the "NPN/PNP" selection button of the test table should be set to the NPN state, and then the positive pole of the diode to be tested is connected to the "C" socket of the test table, and the negative pole is inserted into the "e" of the test table. "The jack, then press the "V (BR)" button, the test meter will indicate the reverse breakdown voltage of the diode. .
Zener diode detection
1. Judgment of positive and negative electrodes From the appearance, the positive end of the metal-packed Zener diode body is flat, and the negative end has a semi-circular shape. One end of the plastically sealed diode body printed with a color mark is a negative electrode, and the other end is a positive electrode. For the Zener diode with unclear mark, it can also be judged by the multimeter. The measurement method is the same as that of the ordinary diode. That is, the multimeter pen is connected to the two electrodes of the Zener diode by the multimeter R×1k file, and one is measured. After the result, the two meter pens were measured. In the two measurement results, the resistance value is smaller, the black meter is connected to the positive pole of the Zener diode, and the red meter is connected to the cathode of the Zener diode. If the positive and negative resistances of the Zener diode are measured to be small or infinite, the diode is broken or open circuit damaged.
2. The measurement of the constant voltage value is 0~30V continuously adjustable DC power supply. For the Zener diode below 13V, the output voltage of the regulated power supply can be adjusted to 15V, and the positive pole of the power supply is connected in series with a 1.5kΩ current limiting resistor. Connected to the negative pole of the measured Zener diode, the negative pole of the power supply is connected to the positive pole of the Zener diode, and then the multimeter is used to measure the voltage across the Zener diode. The measured reading is the regulated value of the Zener diode. If the regulation voltage of the Zener diode is higher than 15V, the regulated power supply should be adjusted to 20V or more.